FIG. 1 illustrates a structure of a backlight in a LCD module. The backlight comprises a liquid crystal panel 1, a protective film 2, an upper prism film 3, a lower prism film 4, a diffusing film 5, a light guiding plate 6 and a bottom reflecting sheet 8 successively from top to bottom. The backlight further comprises a light source 9 located at least one side of the light guiding plate 6, a reflector 10 surrounding the light source 9 and open to the light guiding plate 6, and grids 7 disposed on the bottom surface of the light guiding plate 6. Wherein the protective film 2 may be unnecessary in some backlights. The structure of backlight can be in forms of any combination of the elements mentioned. The backlight is not limited to be applicable to a liquid crystal display device, but can be applicable to other display devices such as an electronic paper etc.
The upper prism film 3 as shown in FIG. 1 is mainly used for converging light. FIG. 2 shows a conventional technology for fabricating the upper prism film; firstly a photoresist is formed on a surface of a substrate which may be composed of macromolecule polymers, for instance, the substrate may be composed of one layer or multi-layers of macromolecule polymers. The macromolecule polymers may be PET (polyethylene terephthalate) etc. The photoresist can be formed on the surface of the substrate by coating, sputtering or depositing, and then passing the substrate through a rotary wheel 13 with prism teeth. The shape defined by adjacent prism teeth on the rotary wheel 13 corresponds to the shape of the prism to be formed, and these prism teeth can form a prism structure on the photoresist. And then the photoresist is cured by a curing light source, such that the substrate and the structures of prism thereon constitute a prism film. For instance, the photoresist may be an UV photoresist, and the curing light source may be an UV curing light source accordingly. It can also adopt photoresists of other types as well as the corresponding curing light sources.
However, the above technology for manufacturing prism film has the following disadvantages in practice: (1) the prism teeth of the rotary wheel are worn and deformed in use, so as to degrade the prism film; (2) when repairing the prism teeth or changing of the prism's parameters such as prism period, modulation depth etc., it needs to process the prism teeth with a machining method such as a laser processing method or a mechanical processing method. However, these processing methods are very complicated, as well as being high-cost and low time-efficient; (3) the modulation depth of the prism structure on the surface of prism film processed by the conventional technology is generally fixed, thereby it can not effectively avoid conglutination between the prism film and other films or the liquid crystal panel.